[Insulin level, glycemia, insulin resistance and β-cell function in relation to the lifestyle of Arctic indigenous people. Are there conditions for diabetes and which type?]

Abstract

Background: Modern studies suggest that lifestyle changes of the indigenous Arctic residents lead to the loss of the "adaptive polar type of metabolism", which is characterized by the intensification of protein metabolism, optimization of lipid metabolism, and minimization of carbohydrate metabolism at low insulin concentrations. How to survive the era of change?

Aim: To assess insulinemia, glycemia, β-cell secretory activity, and insulin sensitivity in Arctic indigenous people in relation to their lifestyle.

Materials and methods: A cross-sectional study of a population of indigenous Arctic residents (Nenets, Komi) aged from 22 to 60 years was conducted. Insulin levels were studied in blood serum using ELISA, and glucose levels using the spectrophotometric method. Insulin resistance (HOMA-IR) and β-cell function (HOMA1-%β) indices were calculated.

Results: 397 people were examined; 89 (22%) of them were nomadic people (NP) and 44 (49%) were male. Another 308 (78%) were sedentary people (SP), and 69 (22%) were male. The insulin level was significantly lower in NP (6.0 [3.5-11.8] µU/ml) compared to SP (8.3 [4.6-13.1] µU/ml), p=0.006. There was no difference in glycemia (4.6 [4.2-5.0] in NP and 4.6 [4.1-5.2] in SP) between lifestyles.The HOMA-IR was significantly lower in NP (1.3 [0.7-2.4]) than in SP (1.8 [0.95-2.8]), p=0.013. IR-HOMA >2 units was 1.8 times more frequent in the SP than in NP, with adjusted for sex, age, and BMI OR=0.56; 95% CI: 0.33-0.96, p=0.034. The median HOMA1-%β was 128 [67-241] % in NP and 144 [93-236]% in SP with no significant differences between groups. The proportion of individuals with HOMA1-%β <48.9 was 17% in NP versus 5% in SP, p<0.001. The adjusted odds of having HOMA1-%β <48.9 in NP are 3.5 times higher than in SP; 95% CI: 1.56-7.92, p=0.002. Fifty-six cases of glycemia ≥5.6 mmol/l were identified: 13.5% in NP and 14.3% in SP. The ratio IR-HOMA >2/ HOMA1-%β <48.9/BMI was 1.8 units/45%/25.2 kg/m2 in NP and 3.0 units/88%/29.6 kg/m2 in SP.

Conclusion: Maintaining a nomadic lifestyle helps keep lower insulin concentrations; at the same time, glycemic levels in the groups were similar. In the NP group, there was a high proportion of individuals with low β-cell secretory activity, predominantly men; in the SP group, more individuals were insulin-resistant. Analysis of cases of glycemia ≥5.6 mmol/l confirmed, that hyperglycemia in a nomadic lifestyle was associated with β-cell hypofunction and the absence of obesity; on the contrary, in a sedentary lifestyle, it was associated with increased insulin resistance and obesity.